The present invention relates to a method and an apparatus for blowing away particles of glue in a strip gluing unit for folding box or cartons forming machines, wherein a gluing disc is immersed in a glue bath, glue adhering to the gluing disc is metered by a doctor blade and the glue is applied from below to the adhesive flaps of folding box blanks conveyed past.
In a folding box forming machine of the aforementioned type, the folding box blanks are stacked in a feeder and removed individually therefrom. In the strip gluing unit arranged close behind the feeder, the adhesive flaps are glued and in further stations the blanks are folded around scored lines and at the end are folded together so that the adhesive flaps make contact with the opposite side of the blank. The folding boxes lying flat and folded together in this way also travel overlapped through a pressing station, in which they are held under pressure, so that the glue can set.
Boxes which are produced in this way in modern folding box forming machines, have a high travelling speed. Consequently, the gluing disc of the strip gluing unit must rotate very quickly. Due to the geometry resulting from the rectilinear path of movement of the blanks and that of the circular gluing disc, the stream of glue splits in the nip between the path of movement and gluing disc. As a result of adhesion, one branch of the stream of glue remains stuck to the box, for the same reason another branch remains stuck to the gluing disc. This results in a wedge-shaped area in which the association of particles of glue with one or the other branch is uncertain. On account of the high speed of the blanks and gluing disc, these particles are thrown off in the travelling direction and undesirable splashes of glue occur, which contaminate both the blanks as well as subsequent parts in the folding box forming machine and impair their efficiency or even put them out of action. The electronic glue-checking device is particularly sensitive to contamination, the latter device having to be located close behind the strip-gluing unit for technical reasons. For reasons of the orderly production of folding boxes it is therefore absolutely necessary to prevent splashes of glue from reaching the blanks and parts of the machine.
One method of reducing the number of splashes formed consists of increasing the viscosity of the glue. However, this method does not lead to the desired result, since a large number of splashes still remain, which contaminate the parts. Moreover, increasing the viscosity cannot be taken too far, since excessive viscosity reduces the adhesiveness of the glue.